1. Field of the Invention
The invention relates to a pressure glow plug for a diesel engine that comprises a glow plug body for being inserted into a cylinder of the diesel engine, a heating rod that is arranged in the glow plug body and a pressure sensor that is arranged between the heating rod and the glow plug body under a prestress in such a way that the pressure sensor is acted upon by the pressure in the combustion chamber of the cylinder that is transmitted by the heating rod.
2. Description of Related Art
A pressure glow plug of the above-mentioned type is known from published European Patent Application EP 1 096 141 A3.
In this known pressure glow plug, the glow plug body and the heating rod are rigidly connected to one another on the combustion chamber side, and the glow plug body has such a stability that it is able to radially deform in an elastic manner when pressure is applied. The pressure in the combustion chamber of the cylinder acts upon the glow plug body and the heating rod such that the glow plug body that is rigidly seated in the cylinder of the internal combustion engine is elastically deformed while the heating rod is axially displaced relative to the glow plug body. This movement relative to the glow plug body causes the prestressed pressure sensor to be relieved, wherein the difference in the charge state between the prestressed and the relieved state is tapped in the form of a signal for the pressure in the combustion chamber and evaluated.
Such a pressure glow plug serves as a cold-starting aid in order to start the diesel engine at low temperatures and for realizing an intermediate glow function under unfavorable operating conditions, wherein the pressure sensor that may consist, for example, of a piezoelectric ceramic material or a strain gauge makes it possible to obtain information on the combustion process in the cylinder, as well as to evaluate this information and to control the combustion process accordingly. The utilization of such a pressure glow plug results in a diesel engine that can be regulated with respect to the reduction of exhaust gases and the fuel consumption.
However, one disadvantage of known pressure glow plugs is that the transmission of the pressure to the pressure sensor is dependent on the geometry and the stability of the glow plug body.